This invention relates to hypodermic syringes and more particularly to a hypodermic syringe having a protective cap which can be used only one and which may be locked over the needle after the syringe has been used to preclude reuse of the syringe.
With the increase of drug addiction by the intravenous injection of drugs in today's society, and the growth of certain health destroying diseases such as hepatitis and AIDS, which can be transmitted by the multiple use of syringes, it is highly desirable that hypodermic syringes be used only once and either destroyed or discarded in such a state that they are not reusable. Separate devices for destroying a syringe after use involves severing the needle and barrel components and results in the inconvenience of the additional acts of placing the syringe in the device and activating such device. If the syringe is not immediately destroyed in such a device but awaits personel to perform the act, the syringe may escape the normal procedure and be displaced before destruction can occur. Thus, a substantial number of non-reusable syringes have been proposed in the art in recent years.
In my aforesaid copending patent application I have disclosed a non-reusable syringe having a plunger attached to and moveable with an outer barrel, the plunger being received within an inner barrel, and wherein one of the barrels has a pair of longitudinally extending tracks and the other of the barrels has a traveler. The tracks are formed so that the relative movement between the traveler and each track is possible in only one longitudinal direction so that the outer barrel and the plunger may be drawn away from the needle at the end of the inner barrel to charge the inner barrel when the traveler is on one track. Relative rotation of the barrels thereafter drops the traveler onto the other track to permit the plunger to be moved to discharge the inner barrel. Also disclosed is a syringe and a protective cap for use therewith, the syringe having a needle mounting hub including a cam flange on the periphery thereof spaced from the needle end. The cap is positionable on the hub and has a skirt at the open end for receiving the cam flange prior to use of the needle and being removeable therefrom when the syringe is in use. The cap additionally includes an annular cam adjacent the skirt adapted to cooperatively receive the cam flange when the skirt is forced over the cam flange after the syringe has been used but precludes withdrawal of the cam flange thereafter. Thus, the syringe and cap are constructed to permit the cap to be positioned on the hub of the syringe for subsequent removal so that the syringe can be used, and includes a construction which after use of the syringe locks the cap onto the syringe precluding reuse thereof.
Although the apparatus disclosed in the aforesaid patent application provides advantages over the prior art, studies have indicated that most accidental and inadvertent needle pricks result during recapping of a needle. It appears that this may be the main reason why most medical treatment facilities do not re-cap before their disposal even those which may possibly contain infectuous diseases. This practice in failing to follow precautionary re-capping procedures makes it possible to reuse a needle whether inadvertently or by one seeking a needle for illegal use. Additionally, a nonre-capped needle can readily result in accidental pricking as a needle goes through the disposal process.
All the prior art known to the Examiner is disclosed in the aforesaid patent application and in two references cited during the prosecution of that application. The only known art relating to a needle cap is thus disclosed in Lesson et al U.S. Pat. No. 3,890,971 where a plunger and needle cap may be permanently locked after use; in Geiger U.S. Pat. No. 4,121,588 which has a weakened zone for breaking the barrel of the syringe so that the needle stays in the cap; and in the art cited in the aforesaid application.